I don't know a specific email address, but if you go to "My Orders" (located by clicking on the little gear icon in the upper right corner of the website) and then click on the three vertical dots that appear when hovering over an item you'll get an option to "Report a Problem". Maybe you can get help that way?
EDIT: I didn't find this info on the Google Play site so I don't know how accurate it is...
Email:
googleplay-support@google.com
Phone: 855-836-3987 (press 1 then 3)
Phone support is recommended over email according to what I found.